Work is in progress to develop a filter that is capable of selectively eliminating heparin from the bloodstream for use in extracorporeal medical machines. Such an approach would add significantly to the safety of these machines because it would permit heparin to be used in the machine where it is necessary but not in the patient where it is harmful. To achieve this objective, heparinase will be immobilized to a suitable support material. Several studies have been undertaken to develop the filter. Four different assays for heparinase have been developed. These are based on the disappearance of heparin, on the production of heparin degradation products, and on the function of heparin. Heparinase production from flavobacteria has been studied and parameters essential for optimal heparinase production have been identified. These include agitation, temperature, heparin concentration, and fermentation time. Using this information heparinase has been produced with specific activities 50 times higher than in earlier studies. Heparinase purification has been undertaken and the specific activity has been increased nearly 100-fold from the crude cell extract. Goals for the forthcoming year include further studies on enzyme production and purification and exploratory studies on the immobilation of heparinase.